Initial

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/github.com/containerd/containerd/reference/reference.go

@@ -0,0 +1,162 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package reference
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"path"
+	"regexp"
+	"strings"
+
+	digest "github.com/opencontainers/go-digest"
+)
+
+var (
+	// ErrInvalid is returned when there is an invalid reference
+	ErrInvalid = errors.New("invalid reference")
+	// ErrObjectRequired is returned when the object is required
+	ErrObjectRequired = errors.New("object required")
+	// ErrHostnameRequired is returned when the hostname is required
+	ErrHostnameRequired = errors.New("hostname required")
+)
+
+// Spec defines the main components of a reference specification.
+//
+// A reference specification is a schema-less URI parsed into common
+// components. The two main components, locator and object, are required to be
+// supported by remotes. It represents a superset of the naming define in
+// docker's reference schema. It aims to be compatible but not prescriptive.
+//
+// While the interpretation of the components, locator and object, are up to
+// the remote, we define a few common parts, accessible via helper methods.
+//
+// The first is the hostname, which is part of the locator. This doesn't need
+// to map to a physical resource, but it must parse as a hostname. We refer to
+// this as the namespace.
+//
+// The other component made accessible by helper method is the digest. This is
+// part of the object identifier, always prefixed with an '@'. If present, the
+// remote may use the digest portion directly or resolve it against a prefix.
+// If the object does not include the `@` symbol, the return value for `Digest`
+// will be empty.
+type Spec struct {
+	// Locator is the host and path portion of the specification. The host
+	// portion may refer to an actual host or just a namespace of related
+	// images.
+	//
+	// Typically, the locator may used to resolve the remote to fetch specific
+	// resources.
+	Locator string
+
+	// Object contains the identifier for the remote resource. Classically,
+	// this is a tag but can refer to anything in a remote. By convention, any
+	// portion that may be a partial or whole digest will be preceded by an
+	// `@`. Anything preceding the `@` will be referred to as the "tag".
+	//
+	// In practice, we will see this broken down into the following formats:
+	//
+	// 1. <tag>
+	// 2. <tag>@<digest spec>
+	// 3. @<digest spec>
+	//
+	// We define the tag to be anything except '@' and ':'. <digest spec> may
+	// be a full valid digest or shortened version, possibly with elided
+	// algorithm.
+	Object string
+}
+
+var splitRe = regexp.MustCompile(`[:@]`)
+
+// Parse parses the string into a structured ref.
+func Parse(s string) (Spec, error) {
+	u, err := url.Parse("dummy://" + s)
+	if err != nil {
+		return Spec{}, err
+	}
+
+	if u.Scheme != "dummy" {
+		return Spec{}, ErrInvalid
+	}
+
+	if u.Host == "" {
+		return Spec{}, ErrHostnameRequired
+	}
+
+	var object string
+
+	if idx := splitRe.FindStringIndex(u.Path); idx != nil {
+		// This allows us to retain the @ to signify digests or shortened digests in
+		// the object.
+		object = u.Path[idx[0]:]
+		if object[:1] == ":" {
+			object = object[1:]
+		}
+		u.Path = u.Path[:idx[0]]
+	}
+
+	return Spec{
+		Locator: path.Join(u.Host, u.Path),
+		Object:  object,
+	}, nil
+}
+
+// Hostname returns the hostname portion of the locator.
+//
+// Remotes are not required to directly access the resources at this host. This
+// method is provided for convenience.
+func (r Spec) Hostname() string {
+	i := strings.Index(r.Locator, "/")
+
+	if i < 0 {
+		i = len(r.Locator) + 1
+	}
+	return r.Locator[:i]
+}
+
+// Digest returns the digest portion of the reference spec. This may be a
+// partial or invalid digest, which may be used to lookup a complete digest.
+func (r Spec) Digest() digest.Digest {
+	_, dgst := SplitObject(r.Object)
+	return dgst
+}
+
+// String returns the normalized string for the ref.
+func (r Spec) String() string {
+	if r.Object == "" {
+		return r.Locator
+	}
+	if r.Object[:1] == "@" {
+		return fmt.Sprintf("%v%v", r.Locator, r.Object)
+	}
+
+	return fmt.Sprintf("%v:%v", r.Locator, r.Object)
+}
+
+// SplitObject provides two parts of the object spec, delimited by an `@`
+// symbol.
+//
+// Either may be empty and it is the callers job to validate them
+// appropriately.
+func SplitObject(obj string) (tag string, dgst digest.Digest) {
+	parts := strings.SplitAfterN(obj, "@", 2)
+	if len(parts) < 2 {
+		return parts[0], ""
+	}
+	return parts[0], digest.Digest(parts[1])
+}